Blocking/deblocking resin systems for use as a “co-cure-ply” in the fabrication of large-scale composite structure

Abstract

A method for bonding composite structures which includes providing a first and second composite substrate and coupling a co-cure prepreg tape having chemically protected polymerizable functional groups onto a surface of both the first and second composite substrates. The first and second composite substrates are then cured to the co-cure prepreg tape at a first temperature to form a co-cure prepreg tape portion where the first and second composite substrates are fully cured and the co-cure prepreg tape is partially cured. The co-cure prepreg tape portion of the first composite substrate is then coupled to the co-cure prepreg tape portion of the second composite substrate and a deprotection initiator is applied to facilitate deprotection of the chemically protected polymerizable functional groups and cure the co-cure prepreg tape portion of the first and second composite substrates to form a single covalently bonded composite structure.

What is claimed is: 
     
       1. A method for bonding composite substrates comprising:
 providing a first composite substrate and a second composite substrate wherein both the first composite substrate and the second composite substrate are uncured or partially cured and comprise one or more reinforcement fibers and a first curable resin; 
 coupling a co-cure prepreg tape onto a faying surface of both the first and second composite substrates wherein the co-cure prepreg tape comprises a second curable resin having one or more chemically protected polymerizable functional groups; 
 curing the first and second composite substrates to the co-cure prepreg tape at a first temperature to form a co-cure prepreg tape portion wherein the first and second composite substrates are fully cured and the co-cure prepreg tape is partially cured; 
 coupling the co-cure prepreg tape portion of the first composite substrate to the co-cure prepreg tape portion of the second composite substrate; 
 applying a second temperature to facilitate deprotection with water and a hydrolysis catalyst of the chemically protected polymerizable functional groups to give unprotected polymerizable functional groups and cure the co-cure prepreg tape portion of the first composite substrate to the co-cure prepreg tape portion of the second composite substrate to form a single covalently bonded composite structure. 
 
     
     
       2. The method of  claim 1 , further comprising
 applying a reflow temperature to the co-cure prepreg tape coupled to the first and second composite substrates before curing at the first temperature. 
 
     
     
       3. The method of  claim 1 , wherein:
 the first temperature is from about 75° C. to about 250° C. and the second temperature is from about 75° C. to about 250° C. 
 
     
     
       4. The method of  claim 1 , wherein:
 the first curable resin comprises an epoxide and an amine. 
 
     
     
       5. The method of  claim 1 , wherein:
 the second curable resin comprises an epoxide and a chemically protected polymerizable amine. 
 
     
     
       6. The method of  claim 1 , wherein:
 the one or more chemically protected polymerizable functional groups is an aldimine. 
 
     
     
       7. The method of  claim 1 , wherein:
 the one or more chemically protected polymerizable functional groups is an ketimine. 
 
     
     
       8. The method of  claim 1 , wherein:
 the unprotected polymerizable functional groups are an amine. 
 
     
     
       9. The method of  claim 8 , wherein:
 the amine is 4,6-diethyl-2-methylbenzene-1,3-diamine. 
 
     
     
       10. The method of  claim 1 , wherein:
 the hydrolysis catalyst is selected from the group consisting of acidic alumina, imidazole, and combinations thereof. 
 
     
     
       11. A method for bonding composite substrates comprising:
 providing a co-cure prepreg layer cured to a surface of both a first composite substrate and a second composite substrate wherein the co-cure prepreg layer comprises a chemically protected polymerizable functional group; 
 coupling a portion of the co-cure prepreg layer cured to the first composite substrate to a portion of the co-cure prepreg layer cured to the second composite substrate; 
 applying a deprotection initiator to deprotect the protected polymerizable functional group of the co-cure prepreg layers and to couple the co-cure prepreg layers of the first and second composite substrates, to form a single covalently bonded composite structure. 
 
     
     
       12. The method of  claim 11 , wherein:
 the deprotection initiator comprises a heat source, a chemical reagent, a light source, a mechanical force, or a combination thereof. 
 
     
     
       13. The method of  claim 11 , wherein:
 the first and second composite substrates comprise a curable resin material having an amine and an epoxide. 
 
     
     
       14. The method of  claim 11 , wherein:
 the first and second composite substrates comprise one or more reinforcement fibers. 
 
     
     
       15. The method of  claim 1 , wherein:
 the chemically protected polymerizable functional groups is an aldimine. 
 
     
     
       16. The method of  claim 11 , wherein:
 the chemically protected polymerizable functional groups is an ketimine. 
 
     
     
       17. The method of  claim 11 , wherein:
 the single covalently bonded composite structure comprises a crosslinked amine-cured epoxy polymer network. 
 
     
     
       18. A co-curable composite structure comprising:
 a first and a second uncured or partially cured composite substrate comprising a first curable resin wherein the first curable resin comprises a first epoxide and an amine; 
 a first co-cure prepreg layer coupled to a surface of the first uncured or partially cured composite substrate and a second co-cure prepreg layer coupled to a surface of the second uncured or partially cured composite substrate wherein the first and the second co-cure prepreg layers comprises a second curable resin having a second epoxide and a chemically protected amine; 
 wherein the first and the second uncured or partially cured composite substrate and the first and the second co-cure prepreg layers are cured together at a first temperature until the amines of the first and the second uncured or partially cured composite substrate are functionally fully cured; wherein the first co-cure prepreg layer of the first composite substrate is coupled to the second co-cure prepreg layer of the second composite substrate to form the co-curable composite structure; and 
 wherein the chemically protected amine of the first and the second co-cure prepreg layers are partially cured and remains latent until an additional deprotection and co-cure step. 
 
     
     
       19. The co-curable composite structure of  claim 18 , wherein:
 the chemically protected amine is an aldimine. 
 
     
     
       20. The co-curable composite structure of  claim 18 , wherein:
 the chemically protected amine is a ketimine.